Published online 27 January 2005 | Nature | doi:10.1038/news050124-11

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Ion-drive probe snaps lunar pics

SMART-1 sends first images as it edges towards the Moon.

The craters Brianchon, Pascal and Mouchez, seen from 4,000 kilometres above the Moon's surface.The craters Brianchon, Pascal and Mouchez, seen from 4,000 kilometres above the Moon's surface.© ESA/Space-X, Space Exploration Institute

The European Space Agency probe SMART-1 has returned its first pictures of the Moon's surface.

"This image is the first proof that the camera is working well in lunar orbit," says Jean-Luc Josset of Space-X, the company in Neuchâtel, Switzerland, that built the probe's miniature camera.

The first of the Small Missions for Advanced Research in Technology is also Europe's first lunar mission. It entered a wide orbit around the Moon on 15 November 2004 after a 13-month journey.

The probe uses an innovative propulsion system called an ion drive, where atoms of xenon gas are electrically charged and ejected from the rear of the craft. This produces a gentle forward thrust, roughly equivalent to the weight of a postcard.

The engines have pushed SMART-1 in ever-decreasing loops around the Moon to bring it to 1,000 kilometres from the surface.

A mosaic of images showing the 120-kilometre wide Pythagoras impact crater.A mosaic of images showing the 120-kilometre wide Pythagoras impact crater.© ESA/Space-X, Space Exploration Institute

The Asteroid-Moon Micro-Imager Experiment, which weighs just 450 grams, started taking pictures on 29 December and could identify potential landing sites for robotic or manned landings. Measuring the shadows around the craters will help scientists to work out the height of the crater rims.

The probe also carries instruments that will map the chemicals on the lunar surface. Scientists hope these will reveal more about whether, as most think, the Moon was created more than 3 billion years ago during a collision between another object and the Earth. An infrared spectrometer will hunt for ice deposits in the shadowy interiors of the Moon's deeper craters.

The ion drive has been switched off since 12 January while scientists test SMART-1's instruments and make a medium-resolution survey of the Moon. When the engine is fired up again on 9 February, it will bring the probe to just 300 kilometres above the surface. Five months of scientific investigation will begin on 28 February.